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Germany shuts down seven reactors‎ because of Fokushima

reuters.com

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Re: Germany shuts down seven reactors‎ because of Fokushima

#131

Post by ErrantX »

mironathetin wrote: post #80
mironathetin wrote: post #26

Earlier quoted context omitted.

I still remember the voices after Chernobyl: Light water reactors are safe and core meltdown can never happen, because the moderator is water. If it evaporates, the moderator is gone and the core will cool down. Chernobyl was a graphite moderated reactor. When the core overheated, the graphite melted together with the uranium and the nuclear reaction could not be stopped any more. Now we see how reliable those report…

uvdiv, I did not misunderstand. The light water is the coolant AND the moderator. You need a moderator that slows down the emitted neutrons to keep the nuclear chain reaction going. But evidently, the water is not the only moderator they use. They don't use graphite, though.

But evidently, the water is not the only moderator they use.

Where did you get that assumption from? Water is definitely the only moderator in this form of LWR (based on the published design specs).

Re: Germany shuts down seven reactors‎ because of Fokushima

#132

Post by afterburner »

pjscott wrote: post #130
afterburner wrote: post #125

Earlier quoted context omitted.

"I really do believe that we should be investing in these technologies to make nuclear power safer." This is my major beef with nuclear power. We could invest scads of dollars into expensive and fairly mature nuclear technology, or we can put that same amount of money into renewables which have tremendous room for improvement (that and money towards the advanced power grid that would make renewables also more efficie…

Nuclear technology has a lot of room for improvement, too. There's some improvement that's relatively straightforward, like bringing capital costs down; China is working on this, with great success, as they can now construct CPR1000 plants cheaper than coal plants of the same size. Then we have more exotic and longer-range options, like breeder reactors (both uranium and thorium), small modular reactors, Brayton-cycl…

You know, even if the opportunities for improvement were equal (and that is far from the case; solar power improvements look to be improving by an order of magnitude in the near term, for example), renewables still enjoy a massive safety advantage. So I say save the money and invest in something less fraught with hidden and/or potentially catastrophic costs.

Fact is, even in this still-not-disastrous scenario, there are people working frantically trying to contain the reactors, risking radiation exposure and harm from explosions. If one hundred windmills had fallen over, or 100 solar panels been cracked, there would be no urgency, and the hardware could be replaced easily when it was safe to do so.

Re: Germany shuts down seven reactors‎ because of Fokushima

#133

Post by JohnnyBrown »

eande wrote: post #111
cma wrote: post #57

Earlier quoted context omitted.

Nuclear disasters are so rare that a single data point of the magnitude of damage provides so much information on our risk assessment of nuclear power that it seems reasonable to idle plants while we wait and see how this one plays out. This is only the third major issue to ever happen. Waiting this one out doesn't tell us more about the frequency of occurrence (it already occurred), but it does tell us about the mag…

One nuclear disasters is one too many. If we can't engineer and operate a zero fail nuclear power-plant including various natural desaster scenarios maybe we should not use such technology.

Why would this standard be applied only to nuclear power? Would you say the same about aviation, oil production, dams, or any other highly useful but occasionally dangerous technology?

Re: Germany shuts down seven reactors‎ because of Fokushima

#134

Post by bioh42_2 »

masklinn wrote: post #127
reirob wrote: post #117

Earlier quoted context omitted.

Looking up in http://en.wikipedia.org/wiki/Richter_magnitude_scale the Richter Scale "is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude (shaking amplitude) ...". This means that a Richter magnitude of 9 has a 10 time bigger shaking amplitude than Richter magnitude 8. I do not know for which earthquake magnitude the power plants in Japan were planned but apparent…

Note that the richter scale is outdated, the current scale (while sometimes mis-named Richter) is the Moment Magnitude Scale. It is also a logarithmic scale. Furthermore, as with Richter, > This means that a Richter magnitude of 9 has a 10 time bigger shaking amplitude than Richter magnitude 8 Yes, and a bit above 30 times the energy released (2 magnitudes indicate a thousandfold increase in energy)

Yes, but I think makmanalp point was that earthquakes of up to 8.9 are not unknown in Japan, and there's also been a 9.5 in the world. Thus it would be reasonable to expect 9+ earthquakes and tsunamis in Japan.

Now, can you make anything withstand that? I am not sure, but I think it is possible. It would make electrical power more expensive but how much would more expensive electricity shave of Japan's GDP? Enough to justify not doing it?

Re: Germany shuts down seven reactors‎ because of Fokushima

#135

Post by bioh42_2 »

mortenjorck wrote: post #58
jgrahamc wrote: post #16

Earlier quoted context omitted.

Which beliefs? That a nuclear power station situated in a major earthquake zone next to the coast could magically survive a 9.0 earthquake and a tsunami? Right now, we don't know how serious this situation is, it could be that this will end with a small amount of radiation leaked and four reactors that have to be decommissioned. Or it could end with a major environmental disaster. We simply don't know yet. I'd cautio…

The real tragedy here is that while it's almost certain no civilians will die from radiation poisoning in this case, there quite likely will be or have already been deaths stemming from lack of electrical power. But people dying from illness from lack of clean water because their water treatment plant is offline and their hospital is out of emergency power doesn't get TV ratings, pageviews, and political attention li…

...there quite likely will be or have already been deaths stemming from lack of electrical power.

Last I heard the rolling blackouts were not needed because everyone voluntarily reduced power use. Also planed rolling blackout are designed to be as safe as possible.

But people dying from illness from lack of clean water because their water treatment plant is offline and their hospital is out of emergency power..

This is Japan we're talking about, not Haiti.

The tsunami hit, it was a huge tragedy, but it is over and people are recovering. The nuclear disaster on the other hand is happening as we speak. Naturally people are more interested in the ongoing danger with a great range of possible outcomes.

Re: Germany shuts down seven reactors‎ because of Fokushima

#136

Post by robrenaud »

krschultz wrote: post #54
paganel wrote: post #32

Earlier quoted context omitted.

> That a nuclear power station situation in a major earthquake zone next to the coast could magically survive a 9.0 earthquake and a tsunami? The un-posed question is "what happens if a group of terrorists fly an A380 directly into one of these plants"? Someone on reddit was mentioning that a nuclear plant in Texas was built to "withstand a direct hit from an F-16 traveling at supersonic speeds", but I guess an A380…

K=1/2*mv^2? My intuition (as a mechanical engineer, desinging military systems as my day job) is that the F16 going supersonic is far worse. Either way, there is no possible way you have enough information to make any of the claims you just made. A better question to ask yourself how safe your highway transportation is, because within an hour of my house we've had 15 people killed in bus accidents in the last 72 hour…

My intuition says you are wrong. But I am just a person who liked his high school physics class 10 years ago.

http://en.wikipedia.org/wiki/Airbus_A380

http://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting_...

A380 typical operating weight: 600,000 lb

F16 Loaded weight: 26,500 lb

A380 Max Speed: 580 MPH

F 16 Max Speed: 1500 MPH

Airbus weight advantage ~= factor of 30

F 16 speed advantage ~= factor of 3

3 ^ 2 Maybe there is some destructive value in having the kinetic energy more concentrated in the F16, but a full speed A380 has a lot more kinetic energy than a full speed F16.

Re: Germany shuts down seven reactors‎ because of Fokushima

#138

Post by jonknee »

jedsmith wrote: post #41
jonknee wrote: post #21

Earlier quoted context omitted.

... Which would mean an explosion damaged the containment vessel. The earthquake did remarkably little damage to the plant.

You do realize that everything that has happened at the plant since the earthquake, including that explosion, is a direct result of the earthquake, right? That's like saying the airliners didn't take down the World Trade Center, the fire did. There wouldn't have been a fire if it weren't for the airliners. The earthquake and subsequent effects of the earthquake destroyed these reactors. It's a pointless distinction t…

Of course, but I find your analogy quite poor. All I meant was that the plant [apparently] suffered no damage from the earthquake (which was quite a bit stronger than it had been designed to withstand). It was the tsunami--also larger than the sea wall was designed to withstand--knocking out power that got the plant into its current state. A cache of compatible backup generators that were kept high enough or remotely enough could have prevented this disaster.

Re: Germany shuts down seven reactors‎ because of Fokushima

#139

Post by mironathetin »

ErrantX wrote: post #131
mironathetin wrote: post #80

Earlier quoted context omitted.

uvdiv, I did not misunderstand. The light water is the coolant AND the moderator. You need a moderator that slows down the emitted neutrons to keep the nuclear chain reaction going. But evidently, the water is not the only moderator they use. They don't use graphite, though.

But evidently, the water is not the only moderator they use. Where did you get that assumption from? Water is definitely the only moderator in this form of LWR (based on the published design specs).

I consulted Wikipedia about the design of german light water reactors. Bor is used in addition to water. It enables regulation of the power (in some limits). Makes sense to do that. I don't know if this is done in Japan too. It could explain, why the reaction does not stop after the water is gone.

Re: Germany shuts down seven reactors‎ because of Fokushima

#140

Post by ErrantX »

mironathetin wrote: post #139
ErrantX wrote: post #131

Earlier quoted context omitted.

But evidently, the water is not the only moderator they use. Where did you get that assumption from? Water is definitely the only moderator in this form of LWR (based on the published design specs).

I consulted Wikipedia about the design of german light water reactors. Bor is used in addition to water. It enables regulation of the power (in some limits). Makes sense to do that. I don't know if this is done in Japan too. It could explain, why the reaction does not stop after the water is gone.

Oh I see.

This is a Boiling Water Reactor, a variant of LWR's, it does not use Bor (in any form) as a day-to-day moderator.

However in this incident Boric acid is being added to the water to help with the process.

Pressurized Water Reactors use Boric acid, which is a different variant.

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